mlxsw: reg: Increase register field length to 13 bits

The Infrastructure Entry Delete Register (IEDR) is used to delete
entries stored in the KVD linear database. Currently, it is only
possible to delete entries of size up to 2048. Future firmware versions
will support deletion of entries of size up to 4096.

Increase the size of the field so that the driver will be able to
perform such deletions in the future, when required.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>